Microelectronic circuits for data and/or signal processing contain memories with memory cells that make it possible to store data. As an increasing number of portable systems have come on the market, such as mobile telephones, palm-top computers and medical equipment, the requirements for these memories have become more stringent as processing speed increases. An important example of such memories is the SRAM (Static Random Access Memory), which can be implemented with a small area requirement and allows very rapid access to its content. A static random access memory (SRAM) is a significant memory device due to its high speed, low power consumption, and simple operation. Unlike a dynamic random access memory (DRAM) cell, the SRAM typically does not need to regularly refresh the stored data.
However, SRAM stability is typically impacted by scaling. It is desirable to make the silicon area occupied by the memory cell as small as practical so as to increase the density of the memory array. A memory cell that occupies a small area of silicon permits more memory cells to be fabricated on a single silicon chip of a given size. Hence, there is increasing efforts to scale memory cells and the devices present in memory cells, such as SRAM devices.
Unfortunately, the leakage per area of memory devices, such as SRAM devices, typically increases as device scaling increases. Further, as the device scaling is increased the threshold voltage mismatch (Vth) increases, which typically results in decreased device stability.